A detailed description of the Linux regular expression

Regular Expressions (REGULAR): A set of rules and methods defined for processing a large number of strings,

Common Command Parameters

Basic Regular Expressions

. : There is only one character (including spaces) *: Repeat any of the preceding 0 or more characters. *: matches any character ==> all, including spaces \: Escape character, let meaningful character, display prototype  \$-  -$ itself ^: ^d  file starting with D $:/$  in/End style ^$: Represents a blank line    grep-vn "^$" h.txt-no blank line-  n displays line number  sed-r ' s# (. *) fff#i am \1#g ' h.txt  just take each Line () Something inside    R==reqular[abc]   matches any character in the character set  [0-9] Match 0-9 [A-z] a-z[^abc]  does not match any character in the character set, which is equivalent to taking anti-a\{n,m} Repeat the previous letter, N to M times       grep "0\{2\}" H.txt  repeat 0 2 times     ==>  egrep "0{2}" h.txt ==>  grep-e "0{2}" H.txt \{n,\} repeats   at least n times \{,m\}   repeat more than m times    Note: egrep, Sed-r filter General special characters can not be escaped \w  : print only the letter    grep "\w" H.txt  --A B c d e F g h i \w  : print non-letter \b  : match the delimiter of the word    grep "\bhello\b" h.txt\d  : Represents a number

Common Command Display

Linux grep/egrep Command Detailed

Linux sed command detailed

Linux awk Command Details

Extended Regular Expression

Extended Regular expression: more for Egrep,grep-e     1. + Repeat one or more of the characters         Grep-eo "Go+d" h.txt--god good     2.? Repeat 0 or one  greater range          Grep-eo "G?d" h.txt---  gd, D          grep-eo "Go?d" h.txt--  gd God      3. | Query multiple conforming strings          Grep-eo "Hello|world"--Hello  World    4. () find the "user group" string         egrep "G (la|oo) d" H.txt-good Glad

Some little knowledge about the regular

1.Linux applies To: Grep,egrep,awk,sed,  2. The difference between the wildcards regular,  such as  ls *.log here is the * represents all 3. Linux is generally in the Behavioral Unit 4. Note Character Set export Lc_all=c  

Detailed description of the Linux regular expression